Various organic polymers and monomers often require the addition of stabilizers to protect them from exposure to heat, oxidation or light during processing, storage or final utility thereof. It is known in the art to employ various hydroxylamines in such applications. Thus, for example, in U.S. Pat. No. 3,926,909, Wei teaches the use of dibenzylhydroxylamine and related compounds as stabilizers for spandex and other forms of polyurethanes against discoloration in exposure to combustion fumes, ultraviolet light and smog atmospheres. In such applications, it was found that at least one benzyl group in the hydroxylamine must be present.
Selzer et al., in U.S. Pat. No. 4,590,231, disclose the use of a large number of hydroxylamines as additional stabilizers in polyolefin compositions containing other stabilizers for protection against degradation upon high temperature extrusion, exposure to the combustion products of natural gas, gamma irradiation or upon storage for extended periods.
The use of hydroxylamines is also known as a "shortstop" for terminating free radical polymerizations. Thus, in U.S. Pat. No. 4,409,290 to Wise, diethylhydroxylamine is mentioned as one of many possible shortstop agents for rubbery graft copolymers or overpolymerized copolymers (shell) on a polyacrylate seed (core) which is useful in making glass tire cord adhesives. The adhesives are used to treat glass fiber prior to using the fiber in tire manufacture, wherein the glass fiber has usually been sized with a silane.
A further example of the mention of silanes in connection with hydroxylamines is provided by Kanner in U.S. Pat. No. 4,384,131. In this patent, a process of reacting certain aminofunctional silanes with a stoichiometric amount of an oxime or a hydroxylamine in the presence of a catalyst to form an oximatohydridosilane or an aminohydridosilane is disclosed.
Currently, in the art, various vinylic alkoxysilanes such as methacryloxy and vinylbenzyl functional trialkoxysilanes are stabilized with compounds such as monomethylether of hydroquinone and 4-tert-butylcatechol, respectively. These stabilizers are ordinarily introduced by way of the organic compounds used in the preparation of the alkoxysilanes in order to prevent thermal polymerization of the unsaturated groups thereon. Some of these stabilizers, such as the two mentioned, are activated by oxygen and do not prevent gelation of the alkoxysilane in air-tight containers such as those used in shipping and storage of the product. Moreover, safety considerations often dictate that oxygen levels be kept low during manufacture, storage and use of the alkoxysilanes in view of the potential of fire or explosion. With this observation in mind, some stabilizers which are not activated by oxygen, such as phenothiazine, have been employed but these can promote gelation in certain alkoxysilanes such as N-beta-(N-vinylbenzylaminoethyl)-gamma-aminopropyltrimethoxysilane hydrochloride. These constraints leave few choices in the selection of adequate stabilizing agents for the alkoxysilanes. Therefore, improved stabilizers, which require little oxygen to maintain their activity, are greatly needed.